Dual function feed system for phased-array radar

ABSTRACT

Both a fan and a pencil beam are derived from a single compact radar antenna. The pencil beam is derived from a first r-f source feeding the whole array, and the fan beam is derived from a horn feeding a portion of the array. The source for the pencil beam is reflected from two parallel reflectors onto the array. The reflectors are inclined to the array and have sidewalls between them defining a single-tapered horn. This horn is fed from a second r-f source to feed a fan beam onto the array.

United States Patent [191 Bowman DUAL FUNCTION FEED SYSTEM FOR PHASED-ARRAY RADAR [75 Inventor: David F. Bowman, Moorestown, NJ.

[22] Filed: June 2, 1972 [21] Appl. No.: 259,323

[52] U.S. Cl. 343/729, 343/755, 343/786,

. 343/854 [51] Int. Cl. H0lq 3/26 [58] Field of Search 343/729, 755,786,

[56] I References Cited UNITEDSTATES PATENTS 3,245,081 4/1966 McFarland ..343/755 r ftz a iz 2u l BEAM STEERER l 5 I I RECEIVER 11 3,739,389 June 12, 1973 Primary Examiner-Eli Lieberman Att0rneyHarry M. Saragovitz, Edward J. Kelly, Herbert Her] and Aubrey J. Dunn [5 7] ABSTRACT Both a fan and a pencil beam are derived from a single compact radar antenna. The pencil beam is derived from a first r-f source feeding the whole array, and the fan beam is derived from a horn feeding a portion of the array. The source for the pencil beam is reflected from two parallel reflectors onto the array. The reflectors are inclined to the array and have sidewalls between them defining a single-tapered horn. This horn is fed from a second r-f source to feed a fan beam onto the array.

4 Claims, 1 Drawing Figure TRANSMITTER TR TRANSMITTER Patented June 12, 1973 BEAM STEERER RECEIVER DUAL FUNCTION FEED SYSTEM FOR PI-IASED-ARRAY RADAR SUMMARY OF THE INVENTION This invention is a dual feed system for a phasedarray antenna, such as used for radar. The feed system has first and second parallel reflectors inclined to the plane of the array. A first r-f source provides a pencil beam from reflected illumination off of the reflectors. Walls between the reflectors, together with the reflectors define a horn antenna. This horn is fed by a second r-f source to provide a fan beam on the array.

BRIEF DESCRIPTION OF'TI-IE DRAWING The single figure shows a combined schematic view and side view, with the side portion partly in section, of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawing, element 2 designates the antenna for the phased array. This antenna includes transmit elements 211, phase shifters 4: and receive elements 2b. Obviously 2a and 2b could function as either transmitting or receiving elemmts, elements, for the sake of this invention the radar is assumed to operate in a transmit manner. Array 2 is fed by feed 3 reflected from parallel reflectors 4a and 4b. A pencil beam is formed and directed by proper phasing of phase shifters (1; under control of beam steerer 5. A fan beam is derived from 2 by feeding it with a horn defined by reflectors 4a and 4b with sidewalls between 4a and 4b. The sidewalls are perpendicular .to 4a and 4b and are divergent towards array 2. Sidewall 6 can be seen in the drawing. As can also be seen, 4a and 4b form acute angles with 2, and 4b more closely approaches 2 than does 4a. This leaves a portion of 4b extending beyond the end of the horn formed by the reflectors and the sidewalls. This portion acts as a director or reflector to the beam from the horn and deflects it toward array 2. The horn is fed by probe 7 with energy from transmitter 8 via TR 9. Feed 3 is fed from transmitter 8 via TR 10. Receiver 11 is also connected to TRs 9 and 10. Array 2, feed 3, and all of the elements in dotted line box 12 are all well known in the art and, per se, do not form part of the invention.

While the horn is shown as fed by a probe on a line, a waveguide could be used to feed the horn with a magic-T connected to transmitter 8 and receiver 11. In similar manner, feed 3 could be a double-tapered horn feed from a magic-T also connected to transmitter 8 and receiver 11. Obviously, box 12 could include a switch means to select between the two feed systems. This means is not critical to the invention and could take many forms, such as single-pole, double-throw r-f switches. The invention is in the feed-reflector-horn arrangement as shown in the top portion of the drawing.

I claim:

1. An electromagnetic antenna having an array of elementary antenna elements each including a receiving antenna, a phase shifter and a transmitting antenna, with said receiving and transmitting antennas being in first and second parallel planes, and control means connected to said phase shifters, the improvement comprising: a dual function feed for the antenna including: first and second parallel plane reflectors inclined and adjacent to said first plane; a pencil beam feed for illuminating said array from reflection off of said reflectors; first and second walls between said reflectors; and a fan beam feed feeding the cavity defined by said reflectors and said walls.

2. The antenna as defined in claim 1 wherein said reflectors form an acute angle with the said first plane, said pencil beam feed is within this acute angle, and the first reflector is more distant from the pencil beam feed than the second reflector and more closely approaches the first plane.

3. The antenna as defined in claim 2 wherein said walls are perpendicular to said reflectors and are nonparallel to each other.

4. The antenna as defined in claim 3 wherein said reflectors and said walls define a horn antenna pointing towards said first plane at said acute angle and with a directing section comprised of the portion of said first reflector more closely approaching the first plane, and

with said fan beam feed in the throat of the horn. 

1. An electromagnetic antenna having an array of elementary antenna elements each including a receiving antenna, a phase shifter and a transmitting antenna, with said receiving and transmitting antennas being in first and second parAllel planes, and control means connected to said phase shifters, the improvement comprising: a dual function feed for the antenna including: first and second parallel plane reflectors inclined and adjacent to said first plane; a pencil beam feed for illuminating said array from reflection off of said reflectors; first and second walls between said reflectors; and a fan beam feed feeding the cavity defined by said reflectors and said walls.
 2. The antenna as defined in claim 1 wherein said reflectors form an acute angle with the said first plane, said pencil beam feed is within this acute angle, and the first reflector is more distant from the pencil beam feed than the second reflector and more closely approaches the first plane.
 3. The antenna as defined in claim 2 wherein said walls are perpendicular to said reflectors and are non-parallel to each other.
 4. The antenna as defined in claim 3 wherein said reflectors and said walls define a horn antenna pointing towards said first plane at said acute angle and with a directing section comprised of the portion of said first reflector more closely approaching the first plane, and with said fan beam feed in the throat of the horn. 